Newbie - Help with choosing microcontroller

Hi to all
I am a newbie with arduino. I have used pic18, but I decided to learn something new. I need to choose a microcontroler and a dev. kit. not for something special, but for wide learning of controller and arduino.
help me please with choosing.

If you want to learn about Arduino you would be well served by getting a basic Arduino Uno. You only need a USB cable and the Arduino software so think of it as a development kit.